Prevent RSS folder from being moved into itself

PR #18619.
Closes #18446.

src/base/rss/rss_session.cpp

@@ -185,8 +185,11 @@ nonstd::expected<void, QString> Session::moveItem(Item *item, const QString &des
     if (!result)
         return result.get_unexpected();
 
-    auto srcFolder = static_cast<Folder *>(m_itemsByPath.value(Item::parentPath(item->path())));
     const auto destFolder = result.value();
+    if (static_cast<Item *>(destFolder) == item)
+        return nonstd::make_unexpected(tr("Couldn't move folder into itself."));
+
+    auto srcFolder = static_cast<Folder *>(m_itemsByPath.value(Item::parentPath(item->path())));
     if (srcFolder != destFolder)
     {
         srcFolder->removeItem(item);

src/gui/rss/feedlistwidget.cpp

@@ -105,7 +105,8 @@ FeedListWidget::FeedListWidget(QWidget *parent)
     m_rssToTreeItemMapping[RSS::Session::instance()->rootFolder()] = invisibleRootItem();
 
     m_unreadStickyItem = new FeedListItem(this);
-    m_unreadStickyItem->setData(0, Qt::UserRole, QVariant::fromValue(RSS::Session::instance()->rootFolder()));
+    m_unreadStickyItem->setData(0, Qt::UserRole, QVariant::fromValue(
+            reinterpret_cast<intptr_t>(RSS::Session::instance()->rootFolder())));
     m_unreadStickyItem->setText(0, tr("Unread  (%1)").arg(RSS::Session::instance()->rootFolder()->unreadCount()));
     m_unreadStickyItem->setData(0, Qt::DecorationRole, UIThemeManager::instance()->getIcon(u"mail-inbox"_qs));
     m_unreadStickyItem->setData(0, StickyItemTagRole, true);
@@ -211,9 +212,10 @@ QList<QTreeWidgetItem *> FeedListWidget::getAllOpenedFolders(QTreeWidgetItem *pa
 
 RSS::Item *FeedListWidget::getRSSItem(QTreeWidgetItem *item) const
 {
-    if (!item) return nullptr;
+    if (!item)
+        return nullptr;
 
-    return item->data(0, Qt::UserRole).value<RSS::Item *>();
+    return reinterpret_cast<RSS::Item *>(item->data(0, Qt::UserRole).value<intptr_t>());
 }
 
 QTreeWidgetItem *FeedListWidget::mapRSSItem(RSS::Item *rssItem) const
@@ -275,7 +277,7 @@ QTreeWidgetItem *FeedListWidget::createItem(RSS::Item *rssItem, QTreeWidgetItem
 {
     auto *item = new FeedListItem;
     item->setData(0, Qt::DisplayRole, u"%1  (%2)"_qs.arg(rssItem->name(), QString::number(rssItem->unreadCount())));
-    item->setData(0, Qt::UserRole, QVariant::fromValue(rssItem));
+    item->setData(0, Qt::UserRole, QVariant::fromValue(reinterpret_cast<intptr_t>(rssItem)));
     m_rssToTreeItemMapping[rssItem] = item;
 
     QIcon icon;